Automotive components, having a substantial expanse of metallic material that will vibrate when excited, produce a ringing sound that is not desirable in automobiles. More particularly, a door panel, which is typically formed from sheet metal and has a large span of metallic material, will produce an undesirable ringing sound when closing. This problem has been recognized for many years and a number of attempts have been made to apply a sound deadening material to the inside of the metallic panel in order to deaden the ringing sound that results from the mechanical excitement of the material upon effecting the closing of the door.
One form of deadening material is a single layer of a rubber-based material that is applied to the internal side of the door panel to deaden the ringing sound. Such material will not always provide adequate deadening results. A variation of this type of deadening material is to add a second stiffening member, such as an aluminum panel, applied against the rubber-based material to constrain the sound deadening material between the constraining member and the door panel. While this variation of sound deadening material provides a satisfactory performance, the utilization of this configuration is not optimally adaptable to mass production manufacturing techniques. The provision of a rolled aluminum material would require lift assistance in the assembly line as the roll of material would have a weight greater than 40 pounds and would present difficulties with size for shipping and loading.
In U.S. Pat. No. 4,308,308, granted to Erhard Sachse on Dec. 29, 1981, a two layer sound deadening member is shown where the interior layer is an anti-drumming sheet that has an adhesive layer for attachment to the door panel and a second formed stiffening sheet, which can be formed from fiberglass, that is bonded to the anti-drumming sheet of material. Such sound deadening members are specifically formed for each particular application and do not provide a cost effective alternative for mass production manufacturing techniques.
An extruded thermoplastic material forming part of a water barrier and sound deadening member is disclosed in U.S. Pat. No. 5,456,513, issued to Glen Schmidt on Oct. 10, 1995, for use on automotive door panels. This combination water and sound barrier is formed with a filled plastic material sandwiched between opposing unfilled plastic members, one of which has an adhesive layer for attachment to the door panel. The central filled plastic layer and the opposing unfilled plastic layers can be simultaneously extruded. Such water and sound barrier panels are formed to be attached to specific door panels and, therefore, are not a cost effective alternative for mass production manufacturing techniques.
U.S. Pat. No. 5,094,318, granted to Takashi Maeda on Mar. 10, 1992, discloses a sound absorption material fabricated from various plastic and rubber materials for use in applications such as an automotive dashboard. The moldable plastic constraining material is located between a sound absorbing material and an adhesive dampening sheet formed of a petroleum resin, which can be attached to the dashboard. This integrated member is also preformed for specific installation on particular car components and, therefore, does not present a cost effective alternative for use in mass production manufacturing lines.
A combination of a soundproof material layer and a vibration dampening material layer formed into a sheet is taught in U.S. Pat. No. 4,734,323, issued to Junichi Sato on Mar. 29, 1988. This sheet of material is formed flat. In U.S. Patent Application Publication No. 2002/0170776, published on Nov. 21, 2002, an acoustic layer is placed on a panel that is attached to a door skin by an adhesive. As with the other prior art sound absorption members, this approach does not present a cost effective mass production manufacturing technique.
It would be desirable to provide a two layer sound deadening material that can be pumped into a manufacturing line to be applied in a manner that is conducive to mass production applications.